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Why do jet engines have the swirls on the cones in front?

For lack of technical knowledge on this stuff, I apologize for the vague question words.

I always seem to see large commercial aircraft with those swirls you see popular with hypnotism and such on the turbines. Is there a reason for this, or is it a marketing ploy? And where did it originate?

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  • 10 years ago
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    The swirls make it easier for people to see that the engines are running. This is especially important on the ground because it's crowded and noisy and sometimes it's hard to tell if an engine is running or not.

    There's an urban legend afoot that the swirls are intended to scare birds, but birds really don't care about the swirls.

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  • 10 years ago

    as some others have said it is to show that the engine is running,

    I do know however that it comes from the propeller aircraft. If you look at a prop the tips are painted usually red, if you see a circle than the prop is running, if you can't see the props or a red circle than that plane doesn't have a prop installed. The reason for this is flight lines are very noisy places and with props if they are turning the blades are almost invisible (look at a fast running fan) and it is possible for someone to walk into a turning prop. This is for safety.

    If you want to see this in action take a sharpie and a house fan, draw a line on each blade of the fan and turn that puppy on. The faster you make the fan run the more you will see 1 solid line over the individual blades. If you can make the spiral in the centre of your fan you can see roughly what the jet looks like.

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  • Anonymous
    10 years ago

    It's a safety precaution so that ground staff can see if the engine is turning or not. There where cases where ground equipment or people were sucked into the engine with undesirable results.

    I've no idea where it started though. Just proves that simple ideas are often the best.

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  • 10 years ago

    I never noticed this. There must be an aesthetic reason or the way it swirls when starting shows that it is spinning in the right direction?

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